The present invention relates to a method of measuring blood sugar level for measuring the glucose concentration in blood, and an instrument therefor.
Heretofore, there has been known a blood sugar measuring instrument for measuring the blood sugar level of the blood of a subject by applying blood collected from a finger of the subject to a reagent pad, and by detecting change in color of the reagent pad. In such a blood sugar measuring instrument, light is radiated to the reagent pad, the intensity of reflected light from the reagent pad is measured, and the blood sugar level of the blood applied to the reagent pad is determined.
Change in color of such a reagent pad depends upon the length of time elapsed from the time when the blood was applied to the reagent pad. In the normal practice, therefore, the length of time until the reagent of the reagent pad reacts with glucose in blood is empirically determined, and after the empirically determined time (predetermined time) has elapsed after a subject or a user had instructed the start of measurement, the above-described intensity of reflected light is detected, and the blood sugar level is determined.
In such a method, however, there is dispersion in the length of time after allowing the subject to apply blood to the reagent pad until depressing the switch to instruct the start of measurement. Therefore, even if measurement is started after the predetermined time has elapsed after the start of measurement had been instructed, the result of measurement may include error. Also, if measurement was started after the predetermined time had elapsed considering the delay in time after applying blood to the reagent pad until instructing the start of measurement without using the above-described switch, there was a problem in which the subject or the user always had to wait for longer time resulting in increase in time required for measurement.
An object of the present invention is to provide a method and an instrument for measuring blood sugar level which can measure blood sugar level accurately by automatically determining appropriate timing for measurement, taking the above-described conventional methods and instruments into consideration.
Another object of the present invention is to provide a method and an instrument for measuring blood sugar level which can determine timing for starting measurement automatically corresponding to change in the color of the reagent pad.
Still another object of the present invention is to provide a method and an instrument for measuring blood sugar level which can plainly inform the subject or the user of the process state of blood sugar level measurement.
In order to attain the above objects, the instrument for measuring blood sugar level of the present invention has the following processes:
A blood sugar measuring instrument for measuring the blood sugar level of blood impregnated in a reagent layer of a specimen includes an irradiation mechanism for irradiating light towards the reagent layer, a reflected light detecting device for detecting the intensity of the light reflected from the reagent layer, a calculator for calculating an average value of the intensity per each second, based on the intensity detected by the reflected light detecting device for plural seconds, and a determination device for determining whether or not a change in average values of the intensity calculated by the calculator has become a first predetermined value or less. A blood sugar calculator then calculates the blood sugar level of the blood on the basis of the average value when the determination device determines that the change has become the first predetermined value or less.
According to another aspect of the invention, a method for measuring the blood sugar level of blood impregnated to a reagent layer of a specimen involves directing light toward the reagent, detecting the intensity of light reflected from the reagent, calculating an average value of the intensity each second based on the intensities detected over plural seconds, determining a change in the average value, determining whether the change in the average value has reached a first predetermined value or less, and calculating the blood sugar level of the blood based on the average value when the change in the average value has reached the first predetermined value or less.
Other features and advantages of the present invention will be apparent from the following descriptions taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.